If you've "installed" Eclipse but are having trouble getting it to run, the most likely cause is that you have
not correctly specified the JVM for it to run under. Doing so is easy, just read http://wiki.eclipse.org/Eclipse.ini

Exit Code 13
64-bit Eclipse requires a 64-bit JVM, and 32-bit Eclipse requires 32-bit JVM--you can not mix-and-match
between 32-bit and 64-bit. Mixing 32-bit and 64-bit versions is the most frequent cause of an Error 13, so
make sure the version of Eclipse you installed matches the JVM/JDK that you're using to run it (especially if
you are using eclipse.ini to specify the exact JVM used to run Eclipse, described above). If you are on a 64-bit operating system, the Eclipse
Installer will be looking for a 64-bit Java Runtime.

As a test, open a command line window and run the intended java binary with the -d32 switch to test if it supports 32-bit, or -d64 to test for 64-bit support. It's often
simplest to download a version of Eclipse that will work with whatever Java you already have installed.

To check if you have a 32-bit Java Runtime.:

java -d32 -version

To check if you have a 64-bit Java Runtime.:

java -d64 -version

Java 9 with Eclipse versions prior to Oxygen.1a (Eclipse Platform 4.7.1a)
Java 9 makes substantial changes as to how the classpath is handled in order to add modularity to
Java. For most applications, this is invisible, but it creates issues for Eclipse's own modularity. Oxygen.1a
is the first release of Eclipse that is ready to run under Java 9. If you still have an older Java runtime available,
check the Running Eclipse reference documentation on using the -vm parameter to launch Eclipse and then update to a
compatible version. If you must continue to use an older release, check the Wiki page athttps://wiki.eclipse.org/Configure_Eclipse_for_Java_9 for instructions on adding the
right startup parameters to your eclipse.ini file, script, or shortcut.

If you are trying to run Eclipse on a recent version of macOS, you might encounter an error message that
advises you to install "legacy" Java, with a link to download a very old version of a JRE (1.6). DON'T DO THAT.
It turns out that Apple and OS X has done a thorough job of screwing up what used to be the best OS for
Java development. <sigh/>

The "you need legacy Java" message was from macOS, not Eclipse. The advice to download and install it is
bad advice, but sadly nothing that Eclipse can remedy. Installing "legacy Java" just reverts your system to a
VERY outdated JRE and renders much Java-based software, including Eclipse, broken. <sigh/>

Eclipse requires Java 8 or above, so the best thing is to download JDK 1.8 (not just the JRE) and install
that. In rare cases, you will need, or want, to point your eclipse.ini file to its exact
location per the instructions at the eclipse.ini wiki page. Oracle
JDK download links change often, so it's best to Google for "JDK 8 download" and you'll find it. Here's the
page for Java 8 as it stands at the time I'm writing this. Here's the page for Java 9, which doesn't pose a problem for equally current versions of Eclipse.